A Monte Carlo study of arms effect in myocardial perfusion of normal and abnormal cases utilizing STL heart shape

Arms influence in myocardial perfusion single photon emission computed tomography (SPECT) imaging has been studied for the last two decades. These studies suggested that arms positioning next to the patient would not show cardiac abnormalities or perfusion defects in SPECT imaging while it would not affect the scan during positron emission tomography (PET) scans. As a recent improvement in Geant4 Application for Tomographic Emission (GATE), -a Monte Carlo simulation toolkit- a new feature was added to enable the use of STereoLithography (STL). STL files are implanted as an input geometry for most human organs, which would give superior advantages in details compared to analytical geometry shapes. This study is adopting this recent improvement in GATE to study arms effect in SPECT imaging with the consideration of four scenarios; normal heart perfusion imaging with and without arms positioned next to the patient and two of the same scenarios with a perfusion myocardial defected. The results showed that perfusion defect could be observed with arms next to the patient. For image reconstruction, both filtered backprojection (FBP) and iterative technique - maximum likelihood expectation maximization (MLEM) were used. The MLEM was performed to analyse the four different patient scenarios. The difference in counts between arms-up and arms-down position for the abnormal case was shown to be less than 6%. The conclusion from this paper is that arm influence during abnormal heart SPECT imaging can be measured and has a minimal contribution to the reconstructed images.